Carburetor having a density responsive fuel control



March 1o, 1953 G. E. BEARDSLEY, JR

CARBURETOR HAVING A DENSITY RESPONSIVE FUEL CONTROL.

Filed Feb. l5, 1948 ATTORNEY Patented Mar. 10, 1953 CARBURETOR HAVING A DENSITY RESPONSIVE FUEL CONTROL Guy E. Beardsley, Jr., West Hartford, Conn., as-

signor to United Aircraft' Corporation, East Hartford, Conn., a corporation of Delaware Application February 13, 19,48, Serial No. 8,217

This invention relates to a density sensing device by means of which the density of a medium may be accurately measured. This device may be combined with a control such as the fuel control for power plants.

The use of a sealed expanding chamber in measuring the pressure of the surrounding medium is well known. As such chambers are in the form of sealed bellows, the walls of the expansion chamber have a resiliency that prevents the gas Within the chamber from reaching the same pressure as that of the surrounding medium except when the walls are at rest thereby giving an inaccurate indication of the pressure. The resiliency of the chamber walls also reduces the extent of change in the dimension of the bellows so that the change in the dimension for small changes in pressure is not large enough to be indicated by the device. A feature of this invention is a device for automatically changing the volume of the sealed chamber to maintain the gas pressure within the chamber the same as that of the surrounding medium.

It is well known that a xed mass of gas when sealed in an expansible chamber will always occupy the same volume for a given density. If the chamber is so arranged and located that rapid transfer of heat between the enclosed gas and the surrounding atmosphere is obtained,` the temperatures inside and outside the chamber are maintained alike. With such an arrangement a diierence in density between the medium inside the chamber and the medium outside must be the result of a difference in pressure. If the chamber is caused to change size until there is no pressure differential between the media within and surrounding the chamber, the change in dimension can be used as a measure of the change in density of the medium surrounding the chamber. A feature of the invention is therefore a device for measuring the changes in density of a medium by measuring the changes in size of a sealed chamber resulting 2 claims. (c1. ce1-39)' from changes in the pressure differential between Y on the bellows and causes an error in the density indication. The force available from the bellows, especially in small density changes, is frequently such that the control cannot be moved directly as a result of the change in density. A feature of the invention is a positive means for adjusting the size of the'chamber until the internal and surrounding densities are the same, this positive means producing enough power to actuate the associated control. K

Another feature is the use of this device as a means for adjusting a control mechanism such as the fuel control for an aircraft power plant, thereby adjusting the fuel as a direct function of the density of the medium in which the aircraft power plant is operating.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawing which illustrates an embodiment of the invention.

The figure shows a fuel control for a carburetor with the density indicator associated therewith.

With reference to the single figure, the density responsive device is shown as a device for automatically controlling the fuel to a carburetor as a function of the density ofthe air entering the carburetor. As shown, the induction passage B4 for the carburetor communicates at its inlet end with a chamber 6E in which the density responslve device 68 is located. A throttle 'it may control the flow of air through the induction passage. The induction passage has a large venturi 'I2 which has a surrounding annular chamber 14 communicating with the air inlet through passage 16. A conduit H8 extends from the chamber 14 to a chamber 8B, the outlet of which is controlled by a valve 82 forming a part of the density responsive device, as will hereinafter appear. 82 is located communicates with another chamber 86 connected by a conduit 88 to a chamber 90 forming a part of the fuel control unit 92 for the. carburetor. One wall of the chamber 90 is a diaphragm 94 which is connected to the valve stem 96 of the fuel control unit. The valve stem has associated therewith a valve 93 for ccntrolling the rate of fuel flow through the unit.

On the side of the diaphragm 91S opposite to' the chamber 90 is another chamber Etf! which communicates through a passage |82 with an opening |04 at the throat of a small venturi llll located within the large venturi TZ, thereby applying to the diaphragm 94 the pressure differ- The bore 84 in which the valve ential between the pressure in passage 16 and the pressure at the opening |04.

Fuel enters the fuel control unit through a passage |08 where it may be filtered as by a lter |16 and passes through a channel |I2 to the valve 98. This valve may engage a seat H4, and fuel passing this valve enters a chamber HB on one side of a diaphragm ||8 also connected to the stem 96. From the chamber ||6 Y metered fuel is delivered past a restriction |20 to a conduit |22. On the other side of the diaphragm ||8 is a chamber |24 which is ,connected as by a bypass channel |26 to the metered fuel passage on the downstream Aside .of the restriction i223. An additional small diaphragm |23 may also be attached to the valve stem 96, and the chamber |3 formed by 'this diaphragm may communicate through a small bypass |32 with the chamber IIB. It may be noted that chambers 98 and |66 are also connected by a restricted bypass |34.

With the arrangement above described, the fuel quantity is adjusted as a function of the change in the differential between the pressure at the opening "l and the pressure at the opening lill-l. V'in adapting the device for controlling 'the fuel flow as a function of the density, the valve 82 is connected as by a lever |36 and a link v|38 to a rod hid extending from the lfree end of a sea-led bellows |62 which, as ,above stated, is 1ocated within the chamber '86. As the density varies in the chamber 56, .the vbellows |42 vwill expand or contract and thereby change the position of the valve 82. It may be noted that the valve, which is in the form of a plunger, has 'a tapered end |44 by which to adjust 'the rate-o flow past the valve as 'a function of its position endwise with respect to the end of the :bore 84.

Sealed bellows |42 has one end, the lower end here, fixed to the wall of 'chamber-66. The movable end of the bellows, as has been stated above, is connected through suitable linkage to valve I82 for transmitting motion of the movable end tothe valve. The end of the bellows which is fixed to the Wall-of chamber 66 has-diaphragm |46-clos ing the opening in the bellows, one side of the diaphragm forming one wall of the'chamberrwithin the bellows. The other side of the diaphragm is exposed to a suitable pressure, ,here the pressure ywithin chamber VGli. When ra changeinithe pressure in chamber 'E5 occurs, movement-ofthe diaphragm results. This movement is V`transmitted through suitable linkage, to be described below, l,to actuate a .servo-mechanism which in turn causes movement of the .free end-of the bellows until the pressure .within the bellows `is exactly the same as the rpressure surrounding it. In this way a relatively large movement of .the bellows ,takes place for each change in pressure and a moreaccurate indication of the actual pressure of the surrounding medium results sincethe resiliency of the walls of the bellows or any other resista-nce of the bellows to a change in dimension is eliminated.

The bellows is constructed to transfer heat rapidly between the media inside land outside the bellows so that temperature changes ofthe medium within the bellows may closelyfollow ternperature changes `of the medium outside the bellows. Since a fixed mass of gas will always occupy the same volume for a given `density, and since the temperatures are :maintained thesarne inside and outside the bellows, any differencesin density must be a result of a difference in'pressure. Thus, any changes'findimensionresultlng 4 from pressure changes are also directly related to density changes.

In order that the adjustment of the valve 82 may be made directly as a function of the change in density, a servo-mechanism is provided for actuating the valve and at the same time adjusting the size of the bellows. Diaphragm |46 is connected through a linkage |48 to a valve l which ultimately connects a fuel inlet passage |52 to passages |54 and |56 respectively, leading to Vthe opposite ends of a cylinder |58 in which a piston |50 -on the valve 82 is slideable. When the valve |50 Acollnects either passage |54 or |55 to the fuel inlet, the opposite passage is simultaneously connected to vent channels |52 or |64. The outer side of the diaphragm |46 communicates ,with a chamber |66, communicating as by a passage |68 with the chamber 6E.

As the density of the air in the chamber 5S decreases the diaphragm is forced down, thereby moving the valve |50 up to cause fuel to flow into the upper -end of the cylinder |58 and move the valve B2 down to ldecrease the flow area past the valve 82. The piston EG in cylinder |58 acts as a hydraulic motor to cause upward movement of the free end of :the bellows until the pressure of the lair within the bellows 4is exactly the same as that in the chamber d6. Similarly, an increase in the pressure of the air in chamber 5'6 ,causes upward movement of the Adiaphragm with corresponding upward movement .of the valve 82 and downward movement of the free end of the sealed bellows. The linkage M8 may include an Vadjustment H9. A spring |55 acting on piston |69 will cause the valve |55 to move to open position in case of iailureof .thexdevice ,By `cont;rolling the rate of dow past the valve G2, it is possible to control the pressure differential on Opposite sides of the diaphragm 9d, thereby Yacl-justing or :metering the fuel in response tofdensity changes `in the chamber 65.

`it vis to be understood that the invention `is not limited to the specific `embodiment herein illustrat-ed :and described, but may be used in other Ways without departure from its spirit as dened by the following claims.

1. In a 4device of Vthe class described, a carburetor having a fuel control, a venturi, and density responsive `means for sensing the density of air Aentering' the carburetor and comprising: a Sealed ,expansiblechamber exposed to the air upstream of lthe venturi, the y,chamber lhaving one end xed and being-constructed to transfer heat rapidly so .that temperature changes of the gas Within the chamber closely follow temperature changes of the air surrounding the chamber, a diaphragm closing one end lof the chamber, reversible fmotor means `actuated by movement of thediaphragmfrneans controlled by the reversible motor `means for moving 4the free end of the expansiblechamber `*to change the lvolume of the expansible `chamber and render `the pressure of the gas ,within-the chamberthe same as the pressure of the air surrounding the chamber, and valve means-controlled by movement of the free end of the wipansible chamber,forregulating-the ow of Yfuel throughthe'lfuel control as a function of .the density of the air passing through the carburetor. I'

'2. In a device of the class described, a carburetor having a fuel control, a venturi, and density responsive means for sensing the density ofairentering-the carburetor Yand comprising: a sealed expansrblechamber exposed to the air upstreamof the venturi, Lthe chamber Yhaving one end Xed and being constructed to transfer heat rapidly so that temperature changes of the gas within the chamber closely follow temperature changes of the air surrounding the chamber, a diaphragm closing one end of the chamber, a servomotor actuated by movement of the diaphragm, means controlled by the servomotor for moving the free end of the expansible chamber to change the volume of the expansble chamber and render the pressure of the gas within the chamber` the same as the pressure of the air surrounding the chamber, and valve means controlled by movement of the free end of the expansible chamber for regulating the ow of fuel through the fuel control as a function of the density of the air passing through the carburetor.

GUY E. BEARDSLEY, JR.

REFERENCES CITED The following references are of record in the le of this patent:

Number Number 6 UNITED STATES PATENTS Name Date Brandl May 21, 1935 Adams et al. Mar. 24, 1936 Dallmann July 5, 1938 Beardsley et a1. Jan. 2, 1940 Jacobson Jan. 12, 1943 Hess Oct. 26, 1943 Moore Aug. 14, 1945 Chandler Jan. 15, 1946 Mock Nov. 19, 1946 Nelson Nov. 26, 1946 Kelley Nov. 26, 1946 FOREIGN PATENTS Country Date Switzerland Feb. 1, 1944 

